Character beam-shaped tube



O. F. HAMANN Filed Oct. 9, 1957 Feb. s, 1962 CHARACTER BEAM-SHAPED TUBEAlle 1| This invention relates to improvedcathode-ray tube apparatus forselectively displaying apparatus having predetermined/shapes such ascharacters, symbols, and numerals.

In Patents Nos. 2,735,956, and 2,761,988, for cathoderay apparatus,which patents are issued to Joseph T.

McNaney, there are described character beam-shapedV tubes of the typewherein characters and other intelligible marks may be displayed on thescreen of cathode-ray tube apparatus in a manner to establishintelligible data. The arrangement for obtaining the individualcharacters comprises, within the tube, an aperture mask having aplurality of character-shaped apertures. The aperture'mask is positionedto intercept the electron beam on its way from the electron gun to thecathode-ray tube screen. Sets of deflection voltages are applied todeecting means which direct the electron beam at a selectedcharacter-shaped aperture. The beam passing through the aperture has itscro-ss section shaped to that of the aperture. The character-shaped beamthereafter is deflected onto the cathode-ray tube screen at alocationwhereby, in connection with other previous and succeeding activations ofthe screen phosphor, intelligence is conveyed.

In an application by Joseph T. McNaney, for Radar Identification System,tiled-'September 9, 1957, Serial No. 682,775, now U.S. Patent No.2,976,529, assigned to a common assignee, there is described anarrangement whereby the character beam-shaped tube also has anoncharacter shaped aperture which may be a round hole through which thecathode-ray beam may pass. In this tube, radar data is presented on thescreen of the cathode-ray tube in addition to characters which identifythe target blips on the screen comprising the radar data.

' In the system described and claimed in this McNaney application, apulse is transmitted from a radar transmitter which is reflected from atarget. These targets may be equipped with responding apparatus which,when triggeredvby the transmitter pulse, send back to the receiver apulse code. The pulse code is converted into a set of deilectionpotentials, designated as characterselection potentials. The usual sweeppotentials are obtained from the radar system, and the-beam isintensified at the proper time, whereby the cathode-ray tube screen isilluminated at the proper time to establish theY location of a target.Further, target display informationris withheld until thecharacter-selection potentials have deflected the beam Vto be shapedinto the characters which identify the target. These characters aredisplayed on the screen in association with the target blip.

y, In the operation of the character beam-shaped tube, characters areVilluminated by directing an electron -beam through a particular matrixcharacter and for the optimum character resolution the matr-ix plane isfocused on the viewing screen. The uniformity of ycharacter illuminationis dependent upon the uniformity of emission from the cathode surfaceand the intensity of a displayed character is directly related to thecurrent density of the electron beam as it intercepts the plane of theaperture plate. When the aperture plate has an opening to enable thepresentation of radar information, it was yfound necessary todynamically change the focus of the electron beam from a. large crosssection, which is used to adequately overlap a selected aper- 3,@2AilPatented Feb. 6, 1962 ture, to a small cross section, which is used topresent the radar information. In making the change from large to smallcross section, `and vice versa, it is desirable that the focus be in theplane of the aperture plate. in doing this, the centroid of the beamshifts position, necessitating the use of a corrective signal `appliedto the selection plates.

An object of the present invention is to eliminate the necessity forchanging beam focus when changing the presentation on the cathode-raytube screen from character to radar information.

Another object'of the present invention is to provide a simplearrangement for eliminating a position shift of the centroid of theelectron beam cross section when changing the beam focus in the plane ofthe aperture mask in a character beam-shaped tube.

Yet another object of the present invention is to present uniformlyilluminated characters in a character beamshaped tube regardless of thelack of uniformity lof emission from 4the cathode surface.

Another object of the invention isrto permit the utilization of a matrixhaving smaller intermediate character apertures than possible when acircular beam is used for electron illumination of an aperture.

Another object of the invention is to permit the use of variable sizedcharacters in the matrix.

Still another object of the present invention is the provision of anovel method and means for operating a character beam-shaped tube.

'Theseand other objects of this invention are -achieved in a characterbeam-shaped tube of the type having an aperture plate or matrix in whichthere are apertures having character shapes for shaping the electronbeam, by reducing the be-am cross section in the plane of theaperturemask to be less than that of the aperture and employing raster scantechniques for scanning Ia selected character-shaped aperture.

Thel novel features that are considered characteristic of this inventionare set forth with particularity in the appended claims. The inventionitself, both as to its organization and method, of operation, as well asadditional objects and advantages thereof, will best be understood fromthe following description whenread in connection with the accompanyingdrawings', Vin which:

FGURE l shows a sectional view of a character beamshaped tube of thetype which maybe employed for presenting both radar information andcharacters, together with a block diagram of a system embodying theprinciples of the invention; and

FIGURE 2 `shows a portion of an aperture mask employed in the tube.

Referring now to FIGURE l, there may be seen a cathode-ray tube insection `and l the associated block schematic diagram embodying thisinvention. The cathodedray tube employed in this invention includes anevacuated envelopev l0 within which, at one end, is a cathode l2 withina cont-rol grid 13, which controls the intensity of the electron beamemanated from the cathode i12. A focusing electrode 14 biased from abias source 15 serves the function of focusing the electron beam to havea desired circular cross sectional area at the matrix plane.

Vertical and horizontal pairs` of electrostatic detlectors,

form of symbols, numbers, characters, etc. The purpose of the round holein the aperture plate is to provide for which the lens element 22 issupported. These lens elements are biased to provide an electrostaticfield to form a lens coniiguration, whereby the electron beam will havea curved trajectory. It will enter the field, pass through the selectedaperture, and thereafter it approaches the common axis of the tube andlens as it begins to leave the held. yHorizontal and vertical pairs ofdeflection plates, respectively 2S, 30, are employed to redeflect theelectron ybeam into its path along the axis of the tube after leavingthe iield of iniluence of the lens elements. A detiection yoke 32 isemployed for dellecting the electron beam to. thecorrect position on thescreen il.

Heretofore, when the electron beam was deflected by means of thedeflection plates 16, iti toward a charactershaped aperture, in order toinsure adequate electron illumination of the aperture, a defocusingvoltage was applied to the focusing grid i3. Then, when it was desired'to show radar data, the electron beam was again focused topa spot in theplane of the aperture mask, so that it could pass through the holewhich, in the exemplilication, is positioned in the center of theaperture mask. In accordance with this (invention, there are provided avertical-sweep voltage generator 42 `and ay horizontalsweep voltagegenerator 4G. The sawtooth frequency of the vertical-sweep generator ismade very much smaller than the sawtooth frequency of thehorizontal-sweep generator, for example, on the order of one-tenth ofthe time permitted for a character presentation. Thus, there may be atleast ten raster scans of a character-shaped aperture by an electronbeam. The output of the respective sweep generators 40, d2 areapplied'to two gates, respectively 44, 46. These gates are closed to thepassage of the respective vertical and horizontal sweep voltages untilsuch time as a second input is received from acharacterselection signalsource 47. This second signal is indicative of the fact that a characterselection and presentation is being made. At this time, the respectivegate outputs are applied to a horizontal-scan amplifier 48 and a`vertical-scan amplifier Sil. These amplify the sweep voltages until theywill provide a sutlicient deflection of the beam to adequate cover orscan the selected character-shaped aperture.

The outputs of the respective horizontaland verticalscan ampliers areapplied to the respective vertical and horizontal-dellectors 16, 18,together with the outputs of horizontaland vertical-deflectionamplifiers 52, 54. These deflection amplifiers receive inputs from thecharacter-selection signal source 47, which serve either to deflect theelectron beam toward the central opening in the aperture for radarpresentation or toward a desired character-shaped aperture for characterpresentation. In the absence of selection deflection or raster scansignals, voltages are applied from the character-selection signalsource, which causes the deflectors to deflect the electron beam alongthe tube axis. The combined eifect of the horizontaland vertical-sweepvoltages and the detiection voltages is to cause the electron beam toscan an aperture in the manner of a television scanning raster.

From the above, it will be appreciated that there is no need to changethe focus of the beam when shift-ing from a radar to a characterpresentation, and vice versa. Since the beam is focussed to have a smallcross-sectional area, the elfects of nonuniform cathode emission areobviated. Since it is only desired to affect the electron beam by thesweep voltages only before the beam passes through the apertures, thecoupling between the rst pair of deectors i6, i8 and the second pair ofdeflectors 28, 35) is made through low-pass tilters 6i), 62, whichpermit the regular deection voltages to pass and block the higherfrequency sweep voltages.

The radar transceiver 60, in response to a transmitted pulse, willreceive from a properly equipped target both an echo pulse and a pulsecode representing character identification of the target. A detlectionsignal source 62, in well-known manner, provides the required deflectionsignals, timed by information received from the radar transceiver. Theradar transceivercan also include a from its carrier frequency andapplies it to the character selection signal source 47 for conversionfrom -the digital to analog form required for selecting an aperture inthe aperture plate. For complete'details ofa suitable arrangement,yreference is made to the aforementioned McNaney application.

From the foregoing description, it will be appreciated that there hasbeen described a novel method and means for operating a cathode-ray tubeof the type wherein an electron beam is shaped by passing it through Ianaperture on its way toward the tube screen. The .invention is useful notonly where both Lradar and character prsentations are to be made, butalso where a character presentation alone is to be made, sinceiteffectively overcomes the deleterious effects of nonuniform cathodeemission and permits a more efficient use of the effective matrix area.Y

I claim: r r

l. In a cathode-ray tube display system for displaying characters on thescreen of a cathode-ray tube of the type having an aperture plater withcharacter-shaped apertures for intercepting and shaping the electronbeam cross section, the improvement comprising means for focusing saidelectron beam cross section to have a smaller cross-sectional area thana character-shaped aperture, means for generating verticalandhorizontal-sweep potentials for scanning a character-shaped aperture,means for generating aperture selection voltages, and means to applyboth said verticaland horizontal-sweep potentials and said aperturedeection potentials `to` said electron beam to select and raster scan adesired one of said charactershaped apertures and means for causing theelectrons that traverse said character-shaped aperture to impinge on aviewing screen.

2. ln a cathode-ray tube display system for displaying radar informationand characters on the screen of a cathode-ray` tube of the type havingan aperture plate with character-shaped apertures for intercepting andshaping the electron beam cross section, the improvement comprisingmeans for focusing said electron beam to have a cross-sectional areasmaller than a charactershaped aperture, means for generatingverticaland horizontal-sweep potentials for scanning a character-shapedaperture, means for applying deflection voltages to said electron beamfor presenting radar information and for selecting a desiredcharacter-shaped aperture, and means to apply said sweep potentials tosaid means for applying said deflection voltages to said electron beamonly when a desired character-shaped aperture is selected.

3. `In a cathode-ray tube display system for displaying radarinformation and characters on the screen of a cathode-ray tube of thetype having an aperture plate with character-shaped apertures forintercepting and shaping the electron beam cross section, theimprovement comprising means for lfocusing said electron beam to have across-sectional area smaller than a character-shaped aperture, verticalelectron beam deflecting means, horizontal electron beam deflectingmeans, means for applying a first set of deflection potentials to saidvertical and horizontal electron beam deecting means for presentingradar information, means for applying a second set of one* deflectionpotentials -to said vertical and horizontal electron beam deflectingmeans for selecting desired charactershaped apertures, yand means forrespectively applying said verticaland horizontal-sweep potentials tosaid vertical and horizontal electron beam deecting means only duringthe application of said second set of deflection potentials to rasterscan said selected characters.

4. In a system for presenting on a cathode ray tube both radarinformation from an object and characters corresponding to codedinformation peculiar to said object for identifying portions of saidradar information, said cathode ray tube having a viewing screen,electronemitt'ing means, beam dellection means, and an apertured maskhaving shaping apertures for producing charactershaped displays and anon-shaping aperture for producing a substantially round-shaped display,said cathode ray tube further having a irst fixed-strength electron lensmeans for imaging the electrons from said electron emitting means ontosaid apertured mask in the form of an image substantially smaller thansaid character-shaped apertures, control means for applying deflectionpotentials to said beam deflection means in response to said codedinformation for positioning said imaged beam on an `aperture selected inaccordance with a particular code, said control means further supplyinghorizontal and vertical sweep potentials to said deiiection means forcausing said image to raster-scan the aforesaid selected aperture, meansresponsive to radar information for directing said electron beam throughsaid non-shaping aperture without raster-scanning it, and a secondfixed-strength electron lens means for imaging the .plane of saidaperture mask onto said viewing screenwhereby said irst and secondfixed-strength electron lenses cause clear characters and radar displaysto be produced on said viewing screen.

5. In a system for presenting on a cathode ray tube radar informationfrom an object and characters corresponding to coded informationpeculiar to said object for identifying portions of said radarinformation, said cathode ray tube having a viewing screen, electronemitting means, beam deiiection means, and an apertured mask havingshaping apertures for producing character-shaped displays and anon-shaping aperture for Aproducing a substantially round-shapeddisplay, said beam deflection means being disposed between said emittingmeans and said mask, said cathode ray tube further having a firstfixed-strength electron lens means for imaging the electrons from saidelectron emitting means onto said apertured mask in the form of an imagesubstantially smaller than said character-shaped apertures, controlmeans for supplying deflection potentials to said beam deflection meansin response to said coded information for positioning said imaged beamon an 4aperture selected in accordance with a particular code, saidcontrol means furaperture for producing a substantially round-shaped display; a first fixed-strength electron-lens means Vfor imaging theelectrons from said electron emitting means onto said'y ther supplyingsweep potentials to said beam deflection means for causing said image toraster-scan the aforesaid selected aperture, means responsive to saidradar information for directing said electron beam through saidnonshaping aperture without raster-scanning it, and a secondfixed-strength electron llens means for imaging said 'aperture mask ontosaid viewing screen-whereby said rst and second liXed-strength electronlenses cause clear characters and radar displays to be produced on saidviewing screen.

6. A cathode ray tube for presenting both radai information andcharacters for identifying portions of said radar information,comprising: an evacuated envelope having ia viewing screen and electronemittingmeans;

an apertured mask having character-shaped apertures for producingcharacter-shaped displays and a non-shaping apertured mask in the formof an image substantially smaller than said character-shaped apertures;afsecond iixed-strength electron lens means for imaging saidaperturedlmask onto said viewing screen-whereby said first and secondhired-strength electron lenses cause clear characters and radar displaysto be produced on said viewing screen.

7. A cathode ray tube for presenting a radar display and characters foridentifying portions of said radar display, comprising: an evacuatedenvelope having a viewing screen and electron emitting means; anapertured mask having shaping apertures for producing charactershapeddisplays and a non-shaping aperture for producing a substantiallyround-shaped display; means for causing an image of said electronemitting means to rasterscan a selected aperture, said scanning meanscomprising horizontal and vertical sweep potentials; means for causingsaid image to traverse said non-shaping aperture without raster-scanningit--whereby said first and second .nXed-strength electron lenses cause aradar display and clear characters to be produced on said viewingscreen.

References Cited in the le of this patent UNITED STATES PATENTS2,283,383 McNaney May 19, 1942 2,728,872 Smith Dec. 27, 1955 2,761,988McNaney Sept. 4, 1956 Gilard May 13, 1958

